Stack Trace:
java.lang.IllegalArgumentException: Unable to find a field null with the type com.mojang.authlib.GameProfile in net.minecraft.network.protocol.login.PacketLoginInStart
at ProtocolLib (1).jar//com.comphenix.protocol.reflect.FuzzyReflection.getFieldByType(FuzzyReflection.java:397)
at ProtocolLib (1).jar//com.comphenix.protocol.reflect.accessors.Accessors.getFieldAccessor(Accessors.java:57)
at ProtocolLib (1).jar//com.comphenix.protocol.injector.netty.ChannelInjector.handleLogin(ChannelInjector.java:658)
at ProtocolLib (1).jar//com.comphenix.protocol.injector.netty.ChannelInjector.decode(ChannelInjector.java:591)
at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:529)
at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:468)
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:290)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:346)
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:318)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
at ProtocolLib (1).jar//com.comphenix.protocol.injector.netty.ChannelInjector$2.channelRead(ChannelInjector.java:292)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:346)
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:318)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
at io.netty.handler.timeout.IdleStateHandler.channelRead(IdleStateHandler.java:286)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
at io.netty.handler.flush.FlushConsolidationHandler.channelRead(FlushConsolidationHandler.java:152)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:440)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919)
at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:800)
at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:499)
at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:397)
at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997)
at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
at java.base/java.lang.Thread.run(Thread.java:833)
Dump:
Parameters:
io.netty.buffer.PooledUnsafeDirectByteBuf@35674e64[
memoryAddress=139841249546976
recyclerHandle=io.netty.util.Recycler$DefaultHandle@942ddba
chunk=Chunk(3e6f81f0: 28%, 1155072/4194304)
handle=2251829878456320
memory=java.nio.DirectByteBuffer[pos=0 lim=4194304 cap=4194304]
offset=32768
length=256
maxLength=256
cache=io.netty.buffer.PoolThreadCache@5c7892ef
tmpNioBuf=
allocator=PooledByteBufAllocator(directByDefault: true)
refCnt=2
readerIndex=26
writerIndex=26
markedReaderIndex=0
markedWriterIndex=0
maxCapacity=2147483647
]
manager:
com.comphenix.protocol.injector.PacketFilterManager@2ee92cea[
unhookTask=com.comphenix.protocol.injector.DelayedSingleTask@4cefe927
packetListeners=[PacketAdapter[plugin=UltraCustomizer, sending=ListeningWhitelist[priority=NORMAL, packets=[CHAT[PLAY, SERVER, 15, classNames: [net.minecraft.network.protocol.game.PacketPlayOutChat, net.minecraft.network.protocol.game.ClientboundChatPacket, net.minecraft.network.play.server.SPacketChat] (unregistered)]], gamephase=PLAYING, options=[]], receiving=EMPTY_WHITELIST]]
packetInjector=com.comphenix.protocol.injector.netty.ProtocolInjector$5@54a4b6a4
playerInjection=com.comphenix.protocol.injector.netty.ProtocolInjector$4@2682a4b4
inputBufferedPackets=[]
recievedListeners=com.comphenix.protocol.injector.SortedPacketListenerList@41eb52f2
sendingListeners=com.comphenix.protocol.injector.SortedPacketListenerList@727e3d39
hasClosed=false
classLoader=PluginClassLoader{plugin=ProtocolLib v4.8.0, pluginEnabled=true, url=plugins/ProtocolLib (1).jar}
reporter=com.comphenix.protocol.ProtocolLib$1@4e798695
server=CraftServer{serverName=Paper,serverVersion=git-Paper-457,minecraftVersion=1.19.4}
library=ProtocolLib v4.8.0
asyncFilterManager=com.comphenix.protocol.async.AsyncFilterManager@5609bc4f
knowsServerPackets=true
knowsClientPackets=true
phaseLoginCount=0
phasePlayingCount=1
packetCreation=false
nettyInjector=com.comphenix.protocol.injector.netty.ProtocolInjector@24816632
pluginVerifier=com.comphenix.protocol.injector.PluginVerifier@1d4ee44c
hasRecycleDistance=true
minecraftVersion=(MC: 1.19.4)
debug=false
]
Sender:
com.comphenix.protocol.injector.netty.ChannelInjector@155fcd0[
decodeBuffer=protected void net.minecraft.network.PacketDecoder.decode(io.netty.channel.ChannelHandlerContext,io.netty.buffer.ByteBuf,java.util.List) throws java.lang.Exception
encodeBuffer=protected void net.minecraft.network.PacketEncoder.encode(io.netty.channel.ChannelHandlerContext,java.lang.Object,io.netty.buffer.ByteBuf) throws java.lang.Exception
factory=com.comphenix.protocol.injector.netty.InjectionFactory@478e4117
player=CraftPlayer{name=darkest_wolves}
updated=
playerName=darkest_wolves
playerConnection=
networkManager=net.minecraft.network.NetworkManager@59a4e2ed
originalChannel=[id: 0x421d9545, L:/172.18.0.5:25561 - R:/172.18.0.1:34310]
channelField=VolatileField [accessor=DefaultFieldAccessor [field=public io.netty.channel.Channel net.minecraft.network.NetworkManager.m], container=net.minecraft.network.NetworkManager@59a4e2ed, previous=[id: 0x421d9545, L:/172.18.0.5:25561 - R:/172.18.0.1:34310], current=com.comphenix.protocol.injector.netty.ChannelInjector$3@498f2ba3, previousLoaded=true, currentSet=true, forceAccess=true]
packetMarker={}
currentEvent=
finalEvent=
unfilteredProcessedPackets=com.comphenix.protocol.injector.netty.PacketFilterQueue@6792fd3e
vanillaDecoder=net.minecraft.network.PacketDecoder@195fc8ab
vanillaEncoder=net.minecraft.network.PacketEncoder@33d46158
finishQueue=[]
channelListener=com.comphenix.protocol.injector.netty.ProtocolInjector@24816632
processor=com.comphenix.protocol.injector.NetworkProcessor@733de0f7
injected=true
closed=false
cumulation=PooledUnsafeDirectByteBuf(ridx: 26, widx: 26, cap: 256)
cumulator=io.netty.handler.codec.ByteToMessageDecoder$1@b1fe3d2
singleDecode=false
first=true
firedChannelRead=false
selfFiredChannelRead=true
decodeState=1
discardAfterReads=16
numReads=0
added=true
]
Version:
ProtocolLib v4.8.0
Java Version:
17.0.6
Server:
git-Paper-457 (MC: 1.19.4)

The version you are using does not support 1.19.4. Use the latest dev build (https://ci.dmulloy2.net/job/ProtocolLib/lastSuccessfulBuild/) for partial 1.19.4 support.